DESCRIPTION (from applicant's application) The long-range goal of this proposal is to elucidate the function and significance of monooxygenase-dependent oxidative metabolism (CYP genes) in differentiated skin functions. The general importance of these enzymatic activities is evident from their substrates, which include essential nutrients and growth and differentiation factors (e.g., steroids, retinoids, and fatty acids). The applicant discovered a novel monooxygenase (Cyp2b gene) expressed in the differentiated keratinocytes of embryonic mouse skin. Expression is restricted to this single cell type and is maintained throughout postnatal development. An interdisciplinary approach is proposed to test the hypothesis that a metabolite(s) produced by this enzyme is required to establish the differentiated phenotype or to maintain a differentiated function of these cells. Such a metabolite might participate in intra- or intercellular signalling or in producing a structural component or extracellular product (e.g., epidermal lipids or sebum) of differentiated keratinocytes. The proposed Specific Aims are to: 1 ) clone and characterize novel Cyp2b genes expressed in murine skin and map their expression patterns in situ, 2) express these cDNAs in E. co/i and biochemically characterize the enzymatic activities of the recombinant proteins, and 3) compare the expression and activities of potentially orthologous CYP2B genes expressed in rat skin. These biochemical and molecular data will lead to testable hypotheses of the metabolic pathways in which the cutaneous monooxygenases function in skin in vivo. This proposal is a training vehicle for the applicant to acquire essential expertise in two disciplines: P450 research, mentored by Dr. Michael Waterman, and cutaneous biology mentored by Dr. Lloyd King Jr. The proposed studies will lead to an independent research career for the applicant and important insights into mechanistic aspects of the differentiated functions of keratinocytes.